Scope of Work

This Design/Build project for the City of Defiance consisted of rehabilitating the two existing digesters located at the wastewater treatment plant.

The Mosser Role

Work included replacement of covers, replacement and relocation of biogas flare, recoating anaerobic digesters, replacing digester mixing systems, adding a new pre-cast building to serve the process equipment, and replacing the roof with a new EPDM roof.

The Value of Design-Build

In the design phase, Mosser eliminated the “bells and whistles” from the original requirements. This included eliminating the mag meters and VFDs on the sludge pump motor starters and moving the gas flare control panel inside of the electrical control room instead of being separately mounted in the yard near the gas flare. Mosser also moved the blower enclosures from the east side of the building to the west side for constructability purposes.

Even during the construction phase, modifications were made with the design team to integrate better solutions into the project. Every time an unforeseen condition arose or a value-added idea was thought of, the decision and review process was expedited through the Design-Build process.

Ultimately, these cost-saving measures saved the owner more than 15%.

Those savings realized through Mosser’s more efficient recommendations in the design and construction phases allowed for the addition of the following items to the scope of work. These items still fell within the original budget, coming in even less than competitor bids under two previous Design-Bid-Build RFIs.

  • New membrane roof on the digester building
  • Exterior access hatches on the digester tanks that allow for entry into the tanks without removing the Dystor lids
  • Exterior electrical control building was supplied to eliminate the risk of electrical gear in a hazardous area
  • Replaced the condensation traps on the methane gas lines

“Mosser’s cost-savings recommendations allowed us to add other items to the scope of work, and that was a key factor in them winning the project.”

 Mark Lehnert, Superintendent, City of Defiance Wastewater Treatment plant